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DES Algorithm Steps

The Data Encryption Standard (DES) is a block cipher with 56 bits that uses a unique key to decrypt and encrypt information. The underlying mechanism involves a number of permutations and the shifting of binary data into encrypted format as well as mixing and substitution. The whole process is repeated 16 times in each round, which can confuse the relationship between the original plaintext and the resultant ciphertext in the most effective way possible.

DES isn’t simple to get cracking. Each round entails key-mixing a XOR with a subkey of 48 bits, expansion permutation and S-box-permutation. This is the most crucial aspect of DES’s security. The 32-bit block is divided into 8 parts with a 6-bit number, followed by a set eight nonlinear substitutions known as S-boxes. They are tabulated using an algorithm called f.

After the S-box, the increased right plaintext (RPT), combined with the left text plain (LPT) will produce an ultimate ciphertext of 64 bits. This is the first of a series of XOR operations using a 48-bit key that can be used as the basis for a XOR operation using the original key.

The XOR operation using the 48-bit subkey obscures the original relationship between the plaintext and ciphertext in as far as possible. This is the primary reason behind why DES is extremely secure. The encryption algorithm has additional features, like a counter that increments with each ciphertext that is added, but they are not important in their ability to protect data.

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